The tape shows Taliban military commander Mansoor Dadullah, whose brother was killed by the U.S. last month, introducing and congratulating each team as they stood.

"These Americans, Canadians, British and Germans come here to Afghanistan from faraway places," Dadullah says on the tape. "Why shouldn't we go after them?"

The leader of the team assigned to attack Great Britain spoke in English.

"So let me say something about why we are going, along with my team, for a suicide attack in Britain," he said. "Whether my colleagues, companions and Muslim brothers die today or tonight, every drop of our blood will invigorate the Muslim (unintelligible)."

U.S. intelligence officials described the event as another example of "an aggressive and sophisticated propaganda campaign."

Others take it very seriously.

"It doesn't take too many who are willing to actually do it and be able to slip through the net and get into the United States or England and cause a lot of damage," said ABC News consultant Richard Clarke, the former White House counterterrorism official.